A conventional dispersed multicolor EL lamp is described using its sectional view in FIG. 9. In FIG. 9, the thickness dimension is magnified for illustrative purposes.
In FIG. 9, indium tin oxide, for example, is deposited on a transparent resin film 1 using a deposition method such as vacuum sputtering to form a transparent electrode 2. Then a phosphor layer 3 is formed by dispersing phosphor particles such as zinc sulfide doped with copper in a resin with high dielectric constant such as cyanic resin or fluororubber resin. A dielectric layer 4 is made of the same synthetic resin system as the phosphor layer 3 in which ferroelectric powder such as barium titanate is dispersed. A back electrode layer 5 is made of silver resin system or carbon resin system paste. An insulative cover resist 6, followed by external electrodes 7A and 7B are then formed.
When multicolor text or graphics are displayed using the above conventional EL lamp, the text or graphics are directly drawn onto the surface of the transparent insulative film 1 using optically transmissive color paint; or a sheet on which text or graphics are drawn with optically transmissive color paint is attached to the transparent insulative film 1. Alternatively, the luminescent color of the phosphor layer 3 is partially changed to match the text or graphics.
In the above conventional dispersed multicolor EL lamps, however, only one type of text or graphics can be displayed.